BRICKTIONARY

PAB
LEGO Pick A Brick.

Parts Monkey
One who selflessly finds LEGO elements for another during build time. If building sets, parts monkeys are permitted to help with sub-assemblies, but should be aware that their main duty is to provide the builder with what he/she needs.
"Hey parts monkey - get me some more of those 1x3 plates. And be quick about it - bad monkey."

Patsy
Temporary placeholder. LEGO element used in place of desired piece.
'It's going to be a nice model. I'm waiting on a Bricklink order so I can get rid of those blasted orange patsys...'

Peeper
A hidden piece that shows through the gaps between the bricks, for example a yellow piece inadvertantly showing itself through a black wall.

PF
Power Functions, a 4-wire electrical system introduced in 2007.

POOP
Piece (that can or should be made) Out of Other Pieces. See also SPUD.

A typical POOP - in this case a vehicle chassis moulded in one piece

Poorross
Alternative method of buildng a Ross by putting a technic half-pin in a technic 1x1 brick. However this is a poor substitute for a Ross, thus the term PoorRoss. Incidentally, a PoorRoss has a hole right through the middle and so is genuinely porous, whereas the Ross isn’t. Look, I don't write all of these, so don't blame me if you have a headache now.

Promo
Rare, hard to find promotional LEGO sets.

Promosexual
One who becomes unduly excited when faced with rare, hard to find promotional LEGO sets.